Here are some examples:
* Mountain
* Mountainous
* Mountaineer
* Mountainside
However, there are also other suffixes that can be used, depending on the specific word you want to form. Some examples include:
* -ous: This suffix is used to form adjectives, such as "mountainous" (meaning full of mountains).
* -eer: This suffix is used to form nouns that refer to a person who does something, such as "mountaineer" (meaning a person who climbs mountains).
* -side: This suffix is used to form nouns that refer to the slope or side of something, such as "mountainside" (meaning the slope of a mountain).
Ultimately, the best suffix to use will depend on the specific word you are trying to create.